A MET, or metabolic equivalent of task, is a ratio of a persons working metabolic rate relative to their resting metabolic rate. It is a way to describe the intensity of an exercise or activity, with one MET being the energy you spend sitting at rest. An activity with a MET value of 4 means youre exerting four times the energy than you would if you were sitting still. MET is used to provide general medical thresholds and guidelines to a population, and is primarily designed to be used in epidemiological surveys, where survey respondents answer the amount of time they spend on specific physical activities.
One MET is defined as 1 kcal/kg/hour and is roughly equivalent to the energy cost of sitting quietly. A MET is also defined as oxygen uptake in ml/kg/min with one MET equal to the oxygen cost of sitting quietly, equivalent to 3.5 ml/kg/min. The definition of MET is problematic when used for specific persons, as 1 MET is considered equivalent to the consumption of 3.5 ml O2·kg−1·min−1 (or 3.5 ml of oxygen per kilogram of body mass per minute), and this value may vary depending on the individuals body weight and other factors.
Researchers have assigned MET values to various activities based on the amount of oxygen consumed by the muscles during those activities. This has resulted in a chart of approximate MET values for a variety of light, moderate, and vigorous activities. MET scores are also used to show an individuals level of cardiorespiratory fitness (CRF), or the ability of the heart and lungs to supply oxygen to muscles during physical exertion. Some doctors use MET scores to prescribe exercise for their patients, recommending a certain number of MET minutes per week.
